1. Field of the Invention
This invention relates to an intraocular lens adapted for implantation in the posterior chamber of an eye after intracapsular or extracapsular cataract extraction and more particularly to an intraocular lens having loops extending posteriorly rearward of the lens which are adapted to center the lens within the posterior chamber and wherein the loops engage the posterior capsule while maintaining a spaced relationship between the rear of the lens and the posterior capsule.
2. Description of the Prior Art
In the human eye, a cataract condition results when the tissue within the lens capsule of the eye becomes clouded and obstructs the passage of light. There are two known methods or forms of surgery used to correct this condition; namely, an intracapsular cataract extraction and an extracapsular cataract extraction. In an intracapsular cataract extraction, the entire lens of the eye is removed intact. In such surgery, the zonules or suspensory ligaments about the entire periphery of the capsule, including the posterior capsule, are removed intact such that the occluded material is likewise removed intact. In an extracapsular cataract extraction, the surgeon makes an incision through the annular capsule of the lens and removes the occluded material from the capsule through the incision. In performing the extracapsular cataract extraction, the surgeon may find it necessary to utilize suction, scraping or other techniques to fully extract the clouded cellular material. However, the transparent rear capsule wall of the eye, or the posterior capsule, remains in place in the eye. Also remaining in place are the zonules and the peripheral portions of the anterior capsule, which are generally referred to as the interior capsule flaps.
It is becoming increasingly important for medical and other reasons to perform extracapsular cataract extractions, which are more difficult to perform than an intracapsular cataract extraction. The reasons for extracapsular cataract extractions becoming more desirable is that the posterior capsule remains in place which, in turn, causes the vitreous fluid located behind the posterior capsule to remain in place. If the posterior capsule is removed at the time of surgery, the vitreous fluid, which is a jelly-like material, may rupture through the posterior chamber and into the pupil of the eye, which may result in adverse, undesirable side effects. This complication is generally referred to as "vitreous loss".
Thus, with the increased interest and desire to perform extracapsular cataract extraction, other complications are encountered with respect to the type and structure of the intraocular lens adapted to be located in the posterior chamber of the human eye.
An article entitled "Posterior Chamber Intraocular Lens Implant Centration: In Or Out of `The Bag`" was presented by Samuel L. Pallin, M.D. and Gerald B. Walman, M.D., both of Sun City, Ariz., at the U.S. Intraocular Lens Symposium, Los Angeles, Calif., in April of 1982 and was reprinted in American Intra-Ocular Implant Society Journal, Volume 8, Summer 1982. The article discusses the comparison between 61 posterior chamber lenses implanted using the "in the bag" technique, wherein the basement membranes of the crystalline lens epithelium (the capsule) is the supporting element, and 150 posterior chamber lenses implanted in the ciliary sulcus. The operative results were evaluated to determine the success of centration in each of the two techniques. The article specifically notes the problem of discouraging adhesions of iris tissue to intraocular lenses associated with posterior chamber lenses implanted in the ciliary sulcus.
One known intraocular lens adapted to be positioned in the posterior chamber of the eye is described in U.S. Pat. No. 4,159,546. This intraocular lens is generally referred to as a Shearing-type lens and comprises a plastic lens body having a plurality of flexible and memory retaining non-biodegradable strands, each strand having one end thereof secured to the lens body and with the other lens thereof unsecured and adapted to function as a spring-like strand which may be biased and urged against the ciliary body of the eye to both support, center and fix the lens in position.
Another intraocular lens adapted to be located in the posterior chamber of the eye is described in U.S. Pat. No. 4,244,060. The intraocular lens described in U.S. Pat. No. 4,244,060 includes a lens body and a plurality of lens-centering filaments which extend outwardly in a common plane from spaced rim portions of the lens body. When the filament ends of the intraocular lens are inserted into the cleft of the capsule, the resilience of the filaments function to center the lens behind the pupil. The intraocular lens described in U.S. Pat. No. 4,244,060 includes an annular lip, or ridge, which projects rearwardly from the rear surface of the lens body. The annular lip, or ridge, is adapted to provide a barrier for preventing vitreous fluid from coming forward into the interior chamber in the event a discission surgery has been performed on the posterior capsule, which results in an opening therein and through which vitreous fluid can migrate.
Iolab Corporation offers for sale a Model 103 posterior chamber lens having a disc-shaped lens and a pair of curved loop legs mounted on the rims thereof with one of the models, Model 103L, having the loops extending at an angle commencing near the edge of the rim and in a direction towards the anterior surface of the lens.